The invention relates generally to a novel member of the uteroglobin family of proteins that is over-expressed in a percentage of breast tumors. Furthermore, the invention also relates to reagents and methods for detecting diseases of the breast. More particularly, the present invention relates to reagents such as polynucleotide sequences and the polypeptide sequences encoded thereby, as well as methods which utilize these sequences. The polynucleotide and polypeptide sequences are useful for detecting, diagnosing, staging, monitoring, prognosticating, preventing or treating, or determining predisposition to diseases or conditions of the breast such as breast cancer.
Breast cancer is the most common form of cancer occurring in females in the US. The incidence of breast cancers in the United States is projected to be 180,200 cases diagnosed and 43,900 breast cancer-related deaths to occur during 1997 (American Cancer Society statistics). Worldwide, the incidence of breast cancer has increased from 700,000 in 1985 to about 900,000 in 1990. G. N. Hortobagyi et al., CA Cancer J Clin 45: 199-226 (1995).
Procedures used for detecting, diagnosing, staging, monitoring, prognosticating, preventing or treating, or determining predisposition to diseases or conditions of the breast, such as breast cancer, are of critical importance to the outcome of the patient. For example, patients diagnosed with early breast cancer have greater than a 90% five-year relative survival rate as compared to a survival rate of about 20% for patients diagnosed with distantly metastasized breast cancers. (American Cancer Society statistics). Currently, the best initial indicators of early breast cancer are physical examination of the breast and mammography. J. R. Harris et al. In: Cancer: Principles and Practice of Oncology, Fourth Edition, pp. 1264-1332, Philadelphia, Pa.: J/B. Lippincott Co. (1993). Mammography may detect a breast tumor before it can be detected by physical examination, but it has limitations. For example, the predictive value depends on the observer's skill and the quality of the mammogram. In addition, 80 to 93% of suspicious mammograms are false positives, and 10 to 15% of women with breast cancer have false negative mammograms. C. J. Wright et al., Lancet 346: 29-32 (1995). New diagnostic methods which are more sensitive and specific for detecting early breast cancer are clearly needed.
Breast cancer patients are closely monitored following initial therapy and during adjuvant therapy to determine response to therapy, and to detect persistent or recurrent disease, or early distant metastasis. Current diagnostic procedures for monitoring breast cancer include mammography, bone scan, chest radiographs, liver function tests and tests for serum markers. The serum tumor markers most commonly used for monitoring patients are carcinoembryonic antigen (CEA) and CA 15-3. Limitations of CEA include absence of elevated serum levels in about 40% of women with metastatic disease. In addition, CEA elevation during adjuvant therapy may not be related to recurrence but to other factors that are not clinically important. CA 15-3 can also be negative in a significant number of patients with progressive disease and, therefore, fail to predict metastasis. Both CEA and CA 15-3 can be elevated in nonmalignant, benign conditions giving rise to false positive results. Therefore, it would be clinically beneficial to find a breast associated marker which is more sensitive and specific in detecting cancer recurrence. J. R. Harris et al., supra. M. K. Schwartz, In: Cancer: Principles and Practice of Oncology. Vol. 1, Fourth Edition, pp. 531-542, Philadelphia, Pa.: J/B. Lippincott Co. (1993).
Another important step in managing breast cancer is to determine the stage of the patient's disease because stage determination has potential prognostic value and provides criteria for designing optimal therapy. Currently, pathological staging of breast cancer is preferable over clinical staging because the former gives a more accurate prognosis. J. R. Harris et al., supra. On the other hand, clinical staging would be preferred were it at least as accurate as pathological staging, because it does not depend on an invasive procedure to obtain tissue for pathological evaluation. Staging of breast cancer could be improved by detecting new markers in serum or urine which could differentiate between different stages of invasion. Such markers could be mRNA or protein markers expressed by cells originating from the primary tumor in the breast but residing in blood, bone marrow or lymph nodes and could serve as sensitive indicators for metastasis to these distal organs. For example, specific protein antigens and mRNA, associated with breast epithelial cells, have been detected by immunohistochemical techniques and RT-PCR, respectively, in bone marrow, lymph nodes and blood of breast cancer patients suggesting metastasis. K. Pantel et al., Onkologie 18: 394-401 (1995).
Such procedures also could include assays based upon the appearance of various disease markers in test samples such as blood, plasma, serum or urine obtained by minimally invasive procedures which are detectable by immunological methods. These procedures would provide information to aid the physician in managing the patient with disease of the breast, at low cost to the patient. Markers such as prostate specific antigen (PSA) and human chorionic gonadotropin (hCG) exist and are used clinically for screening patients for prostate cancer and testicular cancer, respectively. For example, PSA normally is secreted by the prostate at high levels into the seminal fluid, but is present in very low levels in the blood of men with normal prostates. Elevated levels of PSA protein in serum are used in the early detection of prostate cancer or disease in asymptomatic men. See, for example, G. E. Hanks et al., In: Cancer: Principles and Practice of Oncology, Vol. 1, Fourth Edition, pp. 1073-1113, Philadelphia, Pa.: J. B. Lippincott Co. (1993); M. K. Schwartz et al., In: Cancer: Principles and Practice of Oncology, Vol. 1, Fourth Edition, pp. 531-542, Philadelphia, Pa.: J. B. Lippincott Co. (1993). Likewise, the management of breast diseases could be improved by the use of new markers normally expressed in the breast but found in elevated amounts in an inappropriate body compartment as a result of the disease of the breast. One example is mammaglobin, a member of the uteroglobin family of proteins, which was only detected in breast tissue. Mammaglobin was also found to be over-expressed in some breast tumors versus normal breast tissue using differential display. M. A. Watson et al., Cancer Res. 56:860-865 (1996).
Further, new markers which could predict the biologic behavior of early breast cancers would also be of significant value. Early breast cancers that threaten or will threaten the life of the patient are more clinically important than those that do not or will not be a threat. G. E. Hanks, supra. Such markers are needed to predict which patients with histologically negative lymph nodes will experience recurrence of cancer and also to predict which cases of ductal carcinoma in situ will develop into invasive breast carcinoma. More accurate prognostic markers would allow the clinician to accurately identify early cancers localized to the breast which will progress and metastasize if not treated aggressively. Additionally, the absence of a marker for an aggressive cancer in the patient could spare the patient expensive and non-beneficial treatment. J. R. Harris et al., supra. E. R. Frykberg et al., Cancer 74: 350-361 (1994).
It would be advantageous, therefore, to provide specific methods and reagents useful for detecting, diagnosing, staging, monitoring, prognosticating, preventing or treating, or determining predisposition to diseases or conditions of the breast. Such methods would include assaying a test sample for products of a gene which are overexpressed in diseases and conditions associated with the breast including cancer. Such methods may also include assaying a test sample for products of a gene which have been altered by the disease or condition associated with the breast including cancer. Such methods may further include assaying a test sample for products of a gene whose distribution among the various tissues and compartments of the body have been altered by a breast-associated disease or condition, including cancer. Such methods would comprise making cDNA from mRNA in the test sample, amplifying, when necessary, portions of the cDNA corresponding to the gene or a fragment thereof, and detecting the cDNA product as an indication of the presence of the disease or condition, including cancer, or detecting translation products of the mRNAs comprising gene sequences as an indication of the presence of the disease. Useful reagents include polynucleotide(s), or fragment(s) thereof which may be used in diagnostic methods such as reverse transcriptase-polymerase chain reaction (RT-PCR), PCR, or hybridization assays of mRNA extracted from biopsied tissue, blood or other test samples; or proteins which are the translation products of such mRNAs; or antibodies directed against these proteins. Such assays would include methods for assaying a sample for product(s) of the gene and detecting the product(s) as an indication of disease of the breast. Drug treatment or gene therapy for diseases and conditions of the breast, including cancer, can be based on these identified gene sequences or their expressed proteins, and efficacy of any particular therapy can be monitored. Furthermore, it would be advantageous to have available alternative, non-surgical diagnostic methods capable of detecting early stage breast disease such as cancer.